Protecting our freshwater

April 4, 2012 - by Heather Amos

Does leaving a buffer between waterways and logging still make sense?

Freshwater streams and lakes are an important lifeline for the ecosystem and urban communities—providing drinking water, power, and habitats for species of all kinds including economically and culturally significant fish like salmon.

Since the 1970s, foresters have left about 30 metres of untouched forest around freshwater streams and lakes in an effort to protect waterways and aquatic ecosystems. But in the past 40 years, few studies have looked at the effectiveness of this practice.

Now the rules are changing; logging companies are cutting closer to waterways. UBC forestry professor John Richardson says the time has come to figure out exactly how wide the buffer should be, where it should be located in the watershed, and whether we should be trying a different strategy.

“Typically policies should be based on research and science. If not, policies should be evaluated after they are implemented,” says Richardson, the head of the Department of Forest Sciences at UBC. “In the case of the 30-metre buffer, we implemented the policy but never tested it.”

The 30-metre buffer used in most of North America, Australia and Europe, was implemented to reduce erosion of the stream-bank, shade the streams to keep temperatures down, protect fish habitats, prevent sediment from accumulating and increase the overall stability of the ecosystem.

In Ontario and Manitoba, foresters are starting to use a strategy called the ‘emulation of natural disturbance,’ where forests may be cut back to the waterline instead of being protected by the 30-metre buffer. Supporters of this new system argue that when a natural disturbance, like a fire, spreads through the landscape, almost nothing is left undisturbed. They believe forest practices should mimic this and this new standard could be adopted elsewhere.

Concerned by the shift in practice, Richardson began in 1998 to study the effectiveness of the 30-metre rule. He compared how streams reacted to various harvesting strategies: a 30-metre buffer, a 10-metre buffer, no trees harvested, every other tree harvested, or clear-cut to the waterline.

“Even after a decade, the stream with the 30-metre buffer was still showing impacts from the harvest when compared to the control stream where no trees were harvested,” says Richardson. Water temperature is still higher and the amount and kinds of small aquatic organisms in the stream, like algae and bacteria, are still different today.

Richardson says, “even with large buffers there is a strong impact on aquatic ecosystems.”

Richardson is not necessarily against using the strategy of emulation of natural disturbance. But in a series of studies published earlier this year with colleagues across Canada, Richardson argues there should be specific studies to test this new strategy before it is widely implemented.

He also suggests that other options for protecting freshwater habitats and quality should be considered.

Some ideas include protecting certain essential river sections, such as areas where a tributary flows in, while leaving other segments less protected. Smaller streams that are more susceptible to landscape change and more easily heated by the sun could also be better protected, while rules for stable larger bodies of water could be more flexible.

Some of Richardson’s colleagues and co-authors on the studies published earlier this year are supportive of the emulation of natural disturbances strategy. They suggest it could be incorporated into forest practices with appropriate guidelines.

“Even after a decade, the stream with the 30-metre buffer was still showing impacts from the harvest.”

Changes to streams can have large
impacts on the ecosystem

Temperature increase

Even a two-degree increase in river temperature can be extremely stressful for salmon, causing some fish to die en route to their spawning area.

Sediment increase

With more sediment in the streams, fine particles travel long distances and can interfere with water treatment, forcing communities to add more chemicals to their drinking water.

Fewer nutrients

In streams that are blocked from the sun by big trees, up to 90 per cent of the food used by the algae and bacteria—the base of the foodweb—come from decomposing leaves, branches and trees in the river. By cutting down all the trees, there is no future supply of energy for those species. There is also no large wood to provide fish a place to hide in streams.